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| Titel |
Deriving solar transient characteristics from single spacecraft STEREO/HI elongation variations: a theoretical assessment of the technique |
| VerfasserIn |
A. O. Williams, J. A. Davies, S. E. Milan, A. P. Rouillard, C. J. Davis, C. H. Perry, R. A. Harrison |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 27, no. 12 ; Nr. 27, no. 12 (2009-12-01), S.4359-4368 |
| Datensatznummer |
250016716
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| Publikation (Nr.) |
 copernicus.org/angeo-27-4359-2009.pdf |
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| Zusammenfassung |
| Recently, a technique has been developed whereby the radial velocity,
Vr, and longitude direction, β, of propagation of an
outward-moving solar transient, such as a Coronal Mass Ejection (CME), can
be estimated from its track in a time-elongation map produced using
Heliospheric Imager (HI) observations from a single STEREO spacecraft. The
method employed, which takes advantage of an artefact of projective
geometry, is based on the evaluation of the best fit of the time-elongation
profile of the transient, extracted from a time-elongation map, to a set of
theoretical functions corresponding to known combinations of radial velocity
and direction; here we present an initial theoretical assessment of the
efficacy of this technique. As the method relies on the manual selection of
points along the time-elongation profile, an assessment of the accuracy with
which this is feasible, is initially made. The work then presented assesses
theoretically this method of recovering the velocity and propagation
direction of solar transients from their time-elongation profiles using a
Monte-Carlo simulation approach. In particular, we assess the range of
elongations over which it is necessary to make observations in order to
accurately recover these parameters. Results of the Monte-Carlo simulations
suggest that it is sufficient to track a solar transient out to around 40°
elongation to provide accurate estimates of its associated radial velocity
and direction; the accuracy to which these parameters can be estimated for a
transient tracked over a particular elongation extent is, however, sensitive
to its velocity and direction relative to the Sun-Spacecraft line. These
initial results suggest that this technique based on single spacecraft
STEREO/HI observations could prove extremely useful in terms of providing an
early warning of a CME impact on the near-Earth environment. |
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